Which non-parametric statistic uses ordinal data to measure monotonic relationships and is analogous to Pearson's r?

Which non-parametric statistic uses ordinal data to measure monotonic relationships and is analogous to Pearson's r?

• A. Chi-square
• B. Mann-Whitney U
• C. Spearman correlation
• D. Wilcoxon Signed Rank

Answer: (C)

The key idea is measuring how two variables relate when you only care about a consistent increasing or decreasing pattern, not necessarily a straight line. Spearman correlation does this by ranking each variable and then computing the usual correlation on those ranks. Because it works on ranks, it doesn’t require interval/ratio data or a linear relationship, so it’s well-suited for ordinal data or when the data aren’t normally distributed. The result, Spearman’s rho, ranges from -1 to 1 and reflects both direction and strength of a monotonic association. Other non-parametric tools either compare groups or test independence without measuring the strength of a monotonic relationship between two variables, so they don’t serve as the analogue to Pearson’s r.

The key idea is measuring how two variables relate when you only care about a consistent increasing or decreasing pattern, not necessarily a straight line. Spearman correlation does this by ranking each variable and then computing the usual correlation on those ranks. Because it works on ranks, it doesn’t require interval/ratio data or a linear relationship, so it’s well-suited for ordinal data or when the data aren’t normally distributed. The result, Spearman’s rho, ranges from -1 to 1 and reflects both direction and strength of a monotonic association.

Other non-parametric tools either compare groups or test independence without measuring the strength of a monotonic relationship between two variables, so they don’t serve as the analogue to Pearson’s r.